Rates of women who are opting for preventive mastectomies, such as Angeline Jolie, have increased by an estimated 50 percent in recent years, experts say. But many doctors are puzzled because the operation doesn't carry a 100 percent guarantee, it's major surgery -- and women have other options, from a once-a-day pill to careful monitoring.

Research by the Stanford School of Medicine concludes that doctors should aggressively examine patients with a moderate to high risk of heart disease to see if such drugs are appropriate. The study was released Monday in the online journal Public Library of Science Medicine.

“Only 50 percent of high-risk patients who visit doctors receive statins,” said study author Dr. Jun Ma, a research associate at the Stanford Prevention Research Center. “People may die prematurely because of inadequate treatment. And people who should receive these drugs but don’t are put at greater risk of heart disease.”

Heart disease is one of the nation’s leading killers, along with cancer. Each year, more than half a million people die from the disease.

Lower lifestyle risksStatins — along with blood-pressure medicines like beta blockers — are critical because they reduce risk factors that cause heart disease. Statins cut cholesterol production in the liver and boost the organ’s ability to remove a “bad” cholesterol known as LDL.

The study also called for a renewed emphasis on how lifestyle factors, including exercise and diet, can reduce heart disease risks. Cholesterol checks are also important for adults.

Dr. Randall Stafford, associate professor of medicine at the Stanford Prevention Research Center and senior author of the study, said risk-lowering lifestyle changes are still overlooked.

“The problem is that we have not been effective at turning this evidence into practice,” he said.

The study is apparently the first to examine how statin therapy varies according to the risk of heart disease among U.S. outpatients.

Researchers examined two national databases that track outpatient visits to hospitals and physicians between 1992 and 2002, and medications prescribed or renewed during the visits.

The researchers compared results with the number of patients who had been diagnosed with high cholesterol levels and varying degrees of risk for heart disease.

Among patients with high cholesterol in moderate and high-risk groups, researchers found fewer than half of patient visits in 2002 ended with a statin recommendation. Use of these drugs overall grew during the decade, but doctors said the drugs were still underused, in particular among moderate-risk patients.

“If compared to the number of patients who would benefit from these drugs, the degree of increase is less than what we’d expect,” Ma said.

The study was funded by Merck Co., which manufactures statins Zocor and Mevacor, and by the Agency for Healthcare Research and Quality.

Dr. Kanu Chatterjee, a cardiologist and medical professor at the University of California, San Francisco, agreed with the findings. He said earlier studies have documented how statins are underused among blacks in the United States and among Europeans.

“There is no question that statins show a tremendous benefit in reducing the rates of heart attack and potentially the risk of strokes,” said Chatterjee, who was not involved with the study.